In digital integrated circuits, buffers are generally divided into two kinds including input buffers and output buffers. One input buffer temporarily stores data sent from peripherals, so as to facilitate a processor removing the data; and one output buffer is used to temporarily store data sent from the processor to the peripherals.
A schematic connection diagram of a currently commonly used output buffer is shown in FIG. 1. A CMOS buffer is composed of an even number of inverters, and a size of a device in each stage is enlarged to improve a driving load capacity of the buffer. After input signals IN and CK pass through a two-input NAND gate, an output P of the two-input NAND gate is taken as an input of the output buffer. The output buffer includes two transistors including a first transistor and a second transistor. The first transistor is a PMOS transistor and is taken as a pull-up transistor. The second transistor is an NMOS transistor and is taken as a pull-down transistor. When a voltage at the point P which is the input of the output buffer is at a high level, the NMOS is turned on and an output voltage OUT is at a low level. When the voltage at the point P which is the input of the output buffer is at the low level, the PMOS is turned on and the output voltage OUT is at the high level.
However, the above CMOS buffer circuit has its own shortcomings: when the input transits from the low level to the high level or from the high level to the low level, the PMOS and the NMOS are simultaneously turned on in a short period of time, at this time, a current is generated from the high level to the low level, resulting in a short-circuit current consumption. A size of the short-circuit current consumption is proportional to the current, a conducting time, a power supply voltage and an input switching frequency. A size of a conduction current in each device is related to sizes of the PMOS and the NMOS. Particularly as an output buffer, each of the pull-up transistor PMOS and the pull-down transistor NMOS has a large width to length ratio, so as to better drive a large load and have a higher fan out capability. However, when each device has a large width to length ratio, the conduction current also becomes large, resulting in that the corresponding short-circuit current consumption becomes large and accounts for a larger proportion of an overall power consumption.